The present invention relates to blood cell counters and more particularly to electronic blood cell counters.
The differential tally is a basic tool used in all medical laboratories during microscopic examination of a prepared blood field for counting and differentiating blood cells. More specifically, the blood to be examined is prepared on a slide, which is then placed under a microscope for examination. For a 100 -cell differential, the laboratory technician then examines the blood and observes 100 blood cells at random. As the slide is examined, the technician counts and accumulates a subtotal for each type of cell encountered. After 100 cells have been counted, the various subtotals provide a percentage indication of the cell types making up the sample.
Differential tallies, both mechanical and electronic, have been developed to facilitate counting of the blood cells observed during the differential count. Typically, such a machine includes six to eight data entry keys each of which is connected to a two-digit display, a separate display showing the total of the two-digit displays (e.g., total number of cells counted), an audible signal generator to sound an alarm when the total count reaches 100. An entry on any one of the data entry keys will increment both the display associated with that key and the "total" display. When the audible signal sounds, indicating that the total count has reached 100, the technician then reads the two-digit displays which then show the percentage of each type of cell observed during the count. Often, the tallies include a "nontotal" key and associated display used to count cells observed during the count which are not to affect the "total" display.
In addition to the described 100-cell differential counts, the technician is often required to perform counts (e.g., spinal fluid counts, platelet counts, and reticulocyte counts) requiring the counting of over 1,000 cells. These differential counts involving large numbers of cells are typically performed using either a hand-held manual counter or a differential tally of the type described above. However, both the hand-held manual counters and known differential tallies require a key depression for the registration on the tally of each cell observed during the count. This method of data entry is extremely laborious, tedious, and boring to the laboratory technician performing the count. Further, error may creep into the count results due to differences between the count occurring in the technician's mind and that being recorded by the technician's fingers.